Silencing apparatus

ABSTRACT

A silencing apparatus comprising a casing; a plurality of silencing tube stages disposed within the casing, each of the stages having silencing tubes arranged parallel to each other and substantially filling a cross-section of the casing and parallel to the flow of gas, each of the stages being displaced longitudinally from each other within the casing; the silencing tubes comprising an outer tube, an inner tube disposed concentrically within the outer tube and leaving an annular space therebetween, and a sound-absorbing material disposed within the annular space; tubes of adjacent stages abutting and communicating in lateral offset relation so that noise-generating gases passing from adjacent stages are continuously divided and subdivided and passed inside and outside of the silencing tube in the second stage; and a third stage of the silencing tube disposed within the casing is displaced from the second stage so that noise of the gas is further modulated and dispersed and passed inside and outside of the silencing tube in the third stage thereby maximizing the area of the sound absorbing material in contact with the noise-generating gas to produce an increased sound-absorbing effect.

' Suzuki [22] Filed. Aug. 1, 1973 [57] ABSTRACT [21] No'zvssissl A silencing apparatus comprising a casing; a plurality I of silencing tube stages disposed within the casing, [52] (L8. Cl. 181/56, 181/50 each of the stages having silencing tubes arranged 51 Int. Cl. F0ln 1/08 parallgl to eagh 19 1 1 3 sglq st n i y filling a cross- [58] Field of Search 181/3 5 R, 35 B, 47, 46,. Section of the casing and parallel to the flow of gas, 1 81/56, 57, 36 C, 71, 72 each of the stages being displaced longitudinally from each other within the casing; the silencing tubes com- [56] References Cited prising an outer tube, an inner tube disposed concen- UNITED STATES PATENTS. trically within the outer tube and leaving an annular 1,844,104 2/1932 Schnell 181/46 x 3 g i smndfabwrbing material 2,738,854 3/1950 Thrower.... 181/36 c i the of adlacem 2,998,860 9/1961 Everett 181,56 X stages abutting and commumcatmg 1n lateral offset re- 3,031,824 5/1962. Cm"t i 0 Isl/56; .lation so that noise-generating gases passing from ad- 3,1.1 1,191 11/1963 Bachert' 181/56 jacent stages are continuously divided and subdivided 3,134,457 5/1964 Marielins 181/56 and passed inside and outside of the silencing tube in 3,159,237 12/1964 Thomas l8I/ C the second stage; and a third stage of the silencing 3 l fis A Bl/56 tube/disposediwithin the-casing is displaced from the 3,776,365 12/1973 Rlchards l8l/5O ,Second Stage so that noise f the gas is further modw FOREIGN PATENTS OR APPLICATIONS lated and dispersed and passed inside and outside of 274,034 0/1963 Australia l8l/5O the silencing tube in the third Stage thereby maximiz' 336,714 10/1930 Great Britain 181/46 ing e fi Of t Sound-absorbing material in Contact 132,663 9 1919 Gr at 5 1 m,, 131/56 with the noise-generating gas, to produce an increased 518,290 11/1955 Canada 181/56 sound-absorbing effect. 949,428 9/1958 Germany l8l/56 1 181,061 11/1935 Switzerland 1131/56 1 Claim, 6 Drawing Figures 1 1o 1 I 1/ ,7' V x I 1' 0 3 3,2? 33:! $.11 1,12; i e's: .a'- 0 0.! 2 132 -21 4 Qwf i '00: o w. I. 0. o o 9 7 l, 0 ogod l at/ 0 l a .Q 0 "1'37: r o p I '0'? o :0 Z b '1' 0 0., O t .Lo 1: '0" ,Q o p l a "I like I0 4|! '1':. '11- I ,1: {no pl. .1: o :.P e a to. a: Q 'ILO t- --'1f; 4 i 0 I 0 A r. '41.? I

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h 0 o .0 o ,a 9 C I 0; I '0 n 0 \JI 0 00' I... (l 1 SILENCING APPARATUS Inventor: Hisao Suzuki, 2 -l-l, Taiheidai Tsujido, Fujisawa-shi, Kanagawa-ken, Japan 1111 3,854,548 [451 Dec. 17, 1974 Primary ExaminerRichard B. Wilkinson Assistant Examiner-Vit W. Miska Attorney, Agent, or Firm-Holman & Stern v PAIENIEUUEBI 7:914.

sum 10F 2 mwmnm PAnimm-ec 111914 saw 20F 2 0 O O O O O O O O ooooooooooooooooooo oo'oooooo oooooooo000000 oooooboooooooooooooo OQOOOOOOOOQOOOOOOOOOOOO 00 000OOOOOOO-OOOOOO OOOO 1 SILENCING APPARATUS BACKGROUND OF THE INVENTION This invention relates to a silencing apparatus to be attached to an axial flow fan of an operating body having a high degree of noise generated therein, for example, a forced blower.

- In view of the fact that a conventional silencing appa- BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described particularly with reference to the accompanuing drawings in which:'

FIG. 1 is an elevational view showing an embodiment of the silencer of the present invention;

FIG. 2 is a plan view cross-sectioned on line ll-Il in G FIG. 3 is an elevational view showing another embodiment; I a 3 FIG. 4 is a plan view cross-ectioned on line IVIV in-FIG. 3; 2 FIG. 5 is a partly sectioned enlarged elevational view of a single silencing tube used in a silencer of FIGS. 1 and}; and I Y t FIG. 6 is a partly sectioned side view of the single silencing tube shown in FIG. 5.

' DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIGS. 5 and 6, an inner tube 4 having many small holes 3 is provided by leaving an annular space between it and an outer tube 2 having many small holes 1. A partition cylinder 5 is interposed concentrically intermediately between the inner tube 4 and outer tube 2, each of annular spaces 6 and 7 being made by dividing the above-mentioned annular space into two with the partition cylinder 5. filled withsoundabsorbing material 8. such as glass wool. The outer tube 2 and inner tube 4am connected with each other at both ends 2 and inner tube 4 are connected with each other at both ends through inwardly axially concerging ring plates 9 to form a silencing tube 10. With reference to FIGS. 2 and4, an inner frame 14 made of a porous plate 13 is provided by leaving a fixed clearnace 12 between it and an outside plate 11.,The clearance '12 is filled with sound-absorbing material 15 such as glas pwool to form a casing 16 opened at both ends. The silencing tubes 1 0,fill the casing 16 as seen in FIGS. 1

and 3.

. Within the inner frame 14 of this casing 16, as shown in FIGS. 1 and 2, a plurality of the peripherally engaged silencing tubes 10 are disposed parallel and fitted as a first stage a in a first plane. Next, a plurality of silencing tubes 10are set parallel andfitted as a second stage b to be in abutting contact with the silencing tubes 10 of the second stage b at one end thereof and displaced laterally by a semicircle. Thus, the mutually parallel, peripherally-engaged silencing tubes 10 are fitted and laterally displaced from each other in several stages a, b, and 0 within thecasing 16 so that a gas-generating noise and having passed through the silencing tubes 10 in the first stage a is dispersed and passes insideand outside the adjacent silencing tubes 10 in the second stage b and is then further dispersed and flows inside and outside the parallel silencing tube 10 in the third stage c.

, 2 and the inner tube 4 which isffilled with soundabsorbing material 8 such as glass wool so that the sound-absorbing material 8 will absorb noises and are formed and are fitted within the casing 16 in connected series. The several stages are displaced from each other so that a gas-generating noise is directed through the parallel silencing tubes 10 in the first stage a in the casing 16 fromthe direction indivated by the arrows in FIG. 2, the gas strikes the silencing tubes 10 next parallel and laterally in the second stage b, and the gas is dispersed and passes both inside and outside the silencing sounds are well absorbed over a wide range. Then, the

sound waves absorbed by the many silencing tubes 10 in the first stage a are further dispersed or modulated and interfered with by the laterally displaced soundabsorbing tubes 10 in the second stage b. The noises (gas streams) are substantially finely divided while flowing inside and outside the many silencing tubes 10 in the second stage b and are silenced by contacting the sound-absorbing material exposed by the perforations 3 etc. Then, the sound waves having passed through the above-mentioned second stage b are again dispersed by the plural silencing tubes 10 and laterally displaced in the third stage 0 gas streams aresubdivided and are passed inside and outside the next adjacent abutting silencing tubes 10. The sound waves that were not silenced by the passage through the silencing tubes in the,

second stage b are absorbed and eliminated by the silencing tubes provided in the third stage c.

In the present invention, as mentioned above, within the casing 16, the silencing tubes 10 are each provided,

with the sound-absorbing material 8 on the peripheral surface in the stages and are displaced from each other. Therefore, the sound waves which contact the surface of the sound-absorbing material 8 is expanded as much as possible, and the sound waves hitting the many silencing tubes are dispersed. Then, the sound waves which are finely divided while being reflected and in- I 'terfered with, pass through the plural silencing tubes 10 and are once more dispersed and pass through the next adjacent, laterally displaced silencing tubes 10 in the 5 series arrangements. Therefore, the sound waves are portions are neither wide nor narrow, but are always the same so that the obstruction to the flow of the exhaust gas is kept as small as possible. Thus, the advantages residing in the present invention are numerous.

What is claimed is: v 1. A silencer for noise-generating gases comprising:

an elongated casing opening axially from end-to-end,

said casing having a closed outer wall and a porous inner wall spaced from the outer wall and a soundabsorbing material disposed therebetween;

a plurality of individual silencing tubes disposed in axially spaced stages extending along the length of said casing, each of the stages of the silencing tubes comprising a plurality of mutually parallel, peripherally engaged individual tubes disposed parallel to the longitudinal axis of the casing and the gases passing therethrough, the plurality of tubes of each of the respective stages substantially filling the cross section of the casing in which they are disposed,

each of the tubes of an upstream stage of tubes being laterally offset so that the longitudinal axis thereof is offset with respect to tubes of a next adjacent stage of tubes, the ends of adjacent tubes of adjacent stages of tubes abutting so that gases leaving an upstream tube pass interiorally and exteriorally of next adjacent tubes of the next adjacent stage of tubes, so that the individual tubes continuously divide the streams of gas entering the casing from the inlet and subdivide and modulate the streams of gas as it moves in individual streams from stage-tostage,

each of the individual tubes comprising concentric, 

1. A silencer for noise-generating gases comprising: an elongated casing opening axially from end-to-end, said casing having a closed outer wall and a porous inner wall spaced from the outer wall and a sound-absorbing material disposed therebetween; a plurality of individual silencing tubes disposed in axially spaced stages extending along the length of said casing, each of the stages of the silencing tubes comprising a plurality of mutually parallel, peripherally engaged individual tubes disposed parallel to the longitudinal axis of the casing and the gases passing therethrough, the plurality of tubes of each of the respective stages substantially filling the cross section of the casing in which they are disposed, each of the tubes of an upstream stage of tubes being laterally offset so that the longitudinal axis thereof is offset with respect to tubes of a next adjacent stage of tubes, the ends of adjacent tubes of adjacent stages of tubes abutting so that gases leaving an upstream tube pass interiorally and exteriorally of next adjacent tubes of the next adjacent stage of tubes, so that the individual tubes continuously divide the streams of gas entering the casing from the inlet and subdivide and modulate the streams of gas as it moves in individual streams from stage-to-stage, each of the individual tubes comprising concentric, perforated, axially spaced sleeves with sound-absorbing material in the space therebetween, said tube sleeves being connected at opposite ends by annular collars converging axially from opposite ends of the individual silencing tubes whereby sound generated by the gases passing through the silencing tubes is absorbed by the sound-absorbing material of the casing and individual tubes as the paths of travel of the gases is continuously altered and frequency is changed from stage-tostage. 